The most frustrating part about writing

The most frustrating part about writing for me is when I start to over thing. I'll over think everything, my topic, paragraph structure, grammar, punctuation. Mostly grammar and punctuation because I can never remember things like is it then or than. I either have too much punctuation or not enough or i use them improperly. Sometimes I find myself stuck and I can't think anymore of what I'm trying to say or the point I'm trying to get across. For a while i could never figure out if I am suppose to capitalize the i's in worlds like I'm and I've but I'm pretty sure I'm suppose to so now I do. I'll get stuck at times trying to figure out if i used a comma correctly, it's where a good bit of my time goes.